In the electronics industry, various operations of mounting and packaging semiconductor chips, such as lead frame bonding operations, are typically sequential in nature. In exemplary apparatus for bonding a ceramic substrate to respective lead terminations at a center of a lead frame, substrates are loaded in sequence onto pedestals on a rotary table and are advanced to a bonding station at which they move into vertical alignment with a corresponding frame of a strip of lead frames to become bonded thereto. The strip itself is incrementally advanced tangentially to the table as the table indexes a new substrate into position.
To achieve alignment repeatedly at the bonding station between the substrates and the respective lead frames a centering station is preferably positioned in prior art apparatus between the position of the table at which the substrates are loaded onto the pedestals and the position at which the substrates are bonded to the respective lead frames. At the centering station the substrates are aligned in reference to a fixed frame of the apparatus. Since the strip of lead frames in incrementally advanced relative to the same fixed frame of the apparatus, an alignment of the substrates with respect to the lead frames appears to be achievable by centering the substrates with respect to the frame.
However, a tendency toward misalignment between the substrates and the respective lead frames has been noted in such prior art lead frame bonding apparatus. The misalignment appears to vary as different pedestals are moved into alignment with the strip. In worst case misalignment conditions, unacceptable bonds between the substrates and the respective lead frames result. It is, therefore, desirable to align the substrates more precisely with respect to the lead frames.